1. Field of the Invention
This invention relates generally to combination spring and washer devices and, more particularly, to a spring and washer device which facilitates pin-type cantilever mounting of a solenoid valve having a plastic body.
2. Description of the Prior Art
U.S. patent application Ser. No. 751,875, filed July 5, 1985 by Ronald G. Davis et al and assigned to the assignee of this invention, describes a solenoid valve particularly suited to automotive transmission applications. The valve has a tubular plastic body in which is disposed a fixed valve orifice and a slidable valve plunger for opening and closing the valve orifice. A solenoid coil for moving the valve plunger is disposed around the tubular plastic body at a first or coil end of the latter. The electromagnetic force (EMF) developed when electric current flows through the coil passes through the tubular plastic body at a flux gap portion of the latter. The wall thickness of the plastic body at the flux gap portion is purposely made as thin as possible to maximize the efficiency of the coil. A second or O-ring end of the tubular plastic body is adapted for insertion into a fluid pressure bore in a support structure such as a transmission control valve body. A mounting strap on a housing around the solenoid coil is adapted for rigid attachment to the support structure whereby the valve is held in the pressure bore and the relatively heavy coil is supported independently of the tubular plastic body.
In automobile transmission applications where available space renders it impractical to use the aforesaid strap mounting arrangement, a pin-type cantilever mounting arrangement may be resorted to as an alternative. In the pin-type cantilever mounting arrangement, the O-ring end of the plastic body is inserted or plugged into the pressure bore with the coil end extending away form the support structure on the opposite side of the flux gap portion from the O-ring end. The tubular plastic body thus functions as a cantilever beam with the coil mass concentrated at its distal end and with the relatively thin walled flux gap portion located between the distal end and the support structure. Fluid pressure forces on the valve urging the tubular plastic body out of the pressure bore are resisted by stationary pins on the support structure which intersect the pressure bore behind a flange on the plastic body. A combination spring and washer device according to this invention, in the aforesaid pin-type cantilever mounting arrangement for a solenoid valve, operates to retard dynamic cantilever beam bending of the plastic body at the flux gap portion and to avoid plastic creep at the interface between the retaining pins and the flange on the plastic body.